Human papillomaviruses and the interferon response.

Human papillomaviruses (HPV) are small DNA viruses that target stratified keratinocytes for infection. A subset of HPV types infect epithelia in the genital tract and are the causative agents of cervical as well as other anogenital cancers. Interferon treatment of existing genital HPV lesions has had mixed results. While HPV proteins down-regulate the expression of interferon-inducible genes, interferon treatment ultimately induces their high-level transcription after a delay. Cells containing complete HPV genomes that are able to undergo productive replication upon differentiation are sensitive to interferon-induced growth arrest, while cells from high-grade cancers that only express E6 and E7 are resistant. Recent studies indicate this sensitivity is dependent upon the binding of the interferon-inducible factor, p56, to the E1 replication protein. The response to interferon by HPV proteins is complex and results from the action of multiple viral proteins.